To study conformational and stabilization changes of a protein macromolecule effected through the specific binding of small molecules, and the relationship of such effects to enzyme catalysis and regulation. Ultracentrifugation, microcalorimetry, spectral, fluorescence, equilibrium binding, and kinetic techniques will be used. In addition, a gel method of zone transport will be standardized for measuring affinity constants of interacting molecules. To study mutual interactions of divalent cations and other effectors with glutamine synthetase from E. coli. Physical and chemical studies of the E. coli ATP: glutamine synthetase adenylyl-transferase will be continued. To purify and characterize the E. coli glutamyl-tRNA synthetase; possible mechanisms for regulating this activity in E. coli will be explored.